For those of you with a 3G, be careful what you wish for. If I wasn't getting an iP4 next week I would downgrade from iOS4(GM) to 3.1.3. Hopefully the release fixes the molasses like interface on the 3G but I doubt it.

Well that may be the case, but I'm still interested in knowing how. Should I restore with a 3.1.3 firmware and then update or might iTunes allow me to update to the public release?

Do NOT try to restore to 3.1.3 it restores, and then goes into recovery mode. It isn't possible to downgrade, I just tried. If you attempt a downgrade it will go into recovery and from there you will have to restore to the iphone os 4 gm again. I'm pretty sure we will be able to plug our phones in on the 21st like any other iphone user and receive the update. While I do not know this for sure, I'm am pretty certain, due to the fact that itunes will not allow you to downgrade. At any rate, here's a similier thread I created about the topic. Hope I helped! If I did, could you please tip the scales! Thanks!

For those of you with a 3G, be careful what you wish for. If I wasn't getting an iP4 next week I would downgrade from iOS4(GM) to 3.1.3. Hopefully the release fixes the molasses like interface on the 3G but I doubt it.

I have a 3G currently running iOS4 jail broken with all features and it is not that bad. It's not fast but it's definitely not that slow on my phone.